using System;
/*
 * $Id: WindowRandomAccessSource.cs 502 2012-12-15 18:17:13Z psoares33 $
 *
 * This file is part of the iText (R) project.
 * Copyright (c) 1998-2012 1T3XT
 * BVBA Authors: Kevin Day, Bruno Lowagie, et al.
 *
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Affero General License version 3 as published by the
 * Free Software Foundation with the addition of the following permission added
 * to Section 15 as permitted in Section 7(a): FOR ANY PART OF THE COVERED WORK
 * IN WHICH THE COPYRIGHT IS OWNED BY 1T3XT, 1T3XT DISCLAIMS THE WARRANTY OF NON
 * INFRINGEMENT OF THIRD PARTY RIGHTS.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Affero General License for more
 * details. You should have received a copy of the GNU Affero General License
 * along with this program; if not, see http://www.gnu.org/licenses or write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA, 02110-1301 USA, or download the license from the following URL:
 * http://itextpdf.com/terms-of-use/
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General License.
 *
 * In accordance with Section 7(b) of the GNU Affero General License, a covered
 * work must retain the producer line in every PDF that is created or
 * manipulated using iText.
 *
 * You can be released from the requirements of the license by purchasing a
 * commercial license. Buying such a license is mandatory as soon as you develop
 * commercial activities involving the iText software without disclosing the
 * source code of your own applications. These activities include: offering paid
 * services to customers as an ASP, serving PDFs on the fly in a web
 * application, shipping iText with a closed source product.
 *
 * For more information, please contact iText Software Corp. at this address:
 * sales@itextpdf.com
 */
namespace iTextSharp.text.io {

    /**
     * A RandomAccessSource that wraps another RandomAccessSouce and provides a window of it at a specific offset and over
     * a specific length.  Position 0 becomes the offset position in the underlying source.
     * @since 5.3.5
     */
    public class WindowRandomAccessSource : IRandomAccessSource {
        /**
         * The source
         */
        private readonly IRandomAccessSource source;
        
        /**
         * The amount to offset the source by
         */
        private readonly long offset;
        
        /**
         * The length
         */
        private readonly long length;
        
        /**
         * Constructs a new OffsetRandomAccessSource that extends to the end of the underlying source
         * @param source the source
         * @param offset the amount of the offset to use
         */
        public WindowRandomAccessSource(IRandomAccessSource source, long offset) : this(source, offset, source.Length - offset) {
        }

        /**
         * Constructs a new OffsetRandomAccessSource with an explicit length
         * @param source the source
         * @param offset the amount of the offset to use
         * @param length the number of bytes to be included in this RAS
         */
        public WindowRandomAccessSource(IRandomAccessSource source, long offset, long length) {
            this.source = source;
            this.offset = offset;
            this.length = length;
        }
        
        /**
         * {@inheritDoc}
         * Note that the position will be adjusted to read from the corrected location in the underlying source
         */
        public virtual int Get(long position) {
            if (position >= length) return -1;
            return source.Get(offset + position);
        }

        /**
         * {@inheritDoc}
         * Note that the position will be adjusted to read from the corrected location in the underlying source
         */
        public virtual int Get(long position, byte[] bytes, int off, int len) {
            if (position >= length) 
                return -1;
            
            long toRead = Math.Min(len, length - position);
            return source.Get(offset + position, bytes, off, (int)toRead);
        }

        /**
         * {@inheritDoc}
         * Note that the length will be adjusted to read from the corrected location in the underlying source
         */
        public virtual long Length {
            get {
                return length;
            }
        }

        /**
         * {@inheritDoc}
         */
        public virtual void Close() {
            source.Close();
        }

        public void Dispose() {
            Close();
        }
    }
}